The present invention relates to a rear suspension structure of an automotive vehicle.
In general, a rear suspension structure in which resilient bushes which are provided at front and rear vehicle-body-side connection portions of a suspension arm are configured to have a small compliance, that is, configured to be hard, is superior in increasing the support rigidity of a rear wheel, thereby providing the quick responsiveness to a steering operation in vehicle cornering, in particular, so that this rear suspension structure is considered to be preferable for the vehicle controllability (handling stability). Meanwhile, there is a problem that the resilient bushes configured to be excessively hard may deteriorate the road-following property or the riding conformability.
Herein, an H-shaped arm as a lower arm which is applied to a conventional rear suspension structure is known as exemplified in European Patent No. 1937498 B2, for example. This H-shaped lower arm is configured to be connected to a vehicle-body side and a wheel side at two points, i.e., front and rear points, on each side, in a vehicle width direction, of a vehicle. Thereby, the H-shaped lower arm can have the superior wheel support rigidity against loads applied in a longitudinal direction, in the vehicle width direction, and in a rotational direction (windup direction).
The H-shaped lower arm disclosed in the above-described patent document is configured such that bush axes of the resilient bushes provided at the front and rear vehicle-body-side connection portions thereof extend obliquely relatively to the vehicle longitudinal direction in a plan view for the reason of setting a pitch center of the rear wheel at an appropriate position from an anti-lift geometry perspective and the like (see an axial line 8a in FIG. 3 of the above-described patent document).
In the above-described structure, however, there is a problem that there may occur twisting at the front and rear vehicle-body-side connection portions of the lower arm which is caused by a longitudinal load transmitted from the rear wheel. Conventionally, in order to suppress the twisting, the resilient bushes provided at the front and rear vehicle-body connection portions are configured to have different properties from each other.
However, in a case where the resilient bushes provided at the front and rear vehicle-body connection portions of the lower arm are configured to have the large compliance in order to suppress the twisting occurring thereat, the vehicle-width-direction compliance of the lower arm becomes so large that there is a concern that a merit of the H-shaped lower arm that the wheel support rigidity of the vehicle width direction (the rigidity against a lateral force) is properly high may be spoiled and thereby the handling stability of the vehicle may not be increased properly.
Meanwhile, in a case where the resilient bushes provided at the vehicle-body connection portions of the lower arm are configured to have the small compliance, i.e., configured to be hard, the road-following property or the riding conformability so deteriorate that there is a concern that the above-described anatomic problem may happen.